1. Field of the Invention
The invention relates to the repair of pallets and, more particularly, to techniques for removing damaged stringers from pallets.
2. Description of the Prior Art
Load-bearing pallets fabricated of wooden components frequently are used to transport and store various articles, machines, or materials. Such pallets generally are of two types: the stringer type and the block type. Stringer-type pallets include three spaced, parallel support members to which upper and lower deckboards are nailed. Block-type pallets employ a number of relatively small, spaced blocks to which upper and lower deckboards are nailed. The spaces between the stringers or the blocks are adapted to receive the tines of conventional forklift trucks.
In the course of being moved from place to place, the pallets frequently become damaged. If a damaged pallet is not repaired, eventually it must be discarded because of its inability to safely and securely support and transport articles or materials. Because a new pallet is expensive, it is desirable to repair damaged pallets rather than to buy new ones, if possible.
Due to the large number of pallets that must be repaired, it is important that high quality pallet repairs be done quickly and inexpensively. Unfortunately, pallet repairs usually are done by hand. That is, damaged pallets must be partially or totally disassembled with crowbars or similar manual tools and reassembled with new components. In the particular case of repairing damaged stringers, the deckboards must be removed or at least separated from the stringers in order to permit any nails that interconnect the deckboards and stringers to be removed or sheared.
Efforts to automate the pallet repair process have not been effective. Mechanized pallet repair to date usually has consisted of the complete dismantlement of the pallets, with the damaged components being discarded and the good components being used to make new pallets. Examples of machines used to dismantle pallets completely are shown in U.S. Pat. Nos. 4,241,495; 4,320,570; 4,945,626; 5,105,526; 5,211,094; 5,243,751; 5,307,554; 5,323,525; 5,414,924, and 5,600,882.
It has been attempted to repair pallets mechanically by removing and replacing only damaged components of the pallets. See U.S. Pat. Nos. 4,750,255 and 5,205,197 for examples of machines that can be used to remove only stringers from pallets. Although the referenced machines attempt to improve the stringer removal process, such machines suffer from a variety of drawbacks.
Many of the referenced machines employ disks that shear, or attempt to shear, the nails that hold the deckboards to the stringers. Usually, two disks cooperate to shear any nails that are encountered. A significant drawback of these devices is that the disks experience rapid wear, thereby increasing the cost of the stringer-removal process as well as increasing downtime due to the need for frequent part replacement or repairs. Furthermore, the disks, even when sharp, do not function to shear the nails as much as to bend the nails and tear them from the stringers or the deckboards. The significant resistance occasioned by advancing the disks through the pallets often leads to breakage of otherwise good pallet components. It is believed that the undesirable performance of prior machines is due to a number of factors, including improper disk design, improper positioning of the disks relative to each other, and excessive flexure of the disks.
Desirably, a stringer removal machine would be available that would enable pallet repairs to be accomplished with a minimum of manual labor and with an increase in processing speed. Hopefully, any such machine would have cutting elements that shears nails effectively without bending them. Such a machine preferably would be sufficiently reliable that part replacement or repairs would be avoided substantially.